C2+ olefins can be used to produce many useful products. For example, ethylene and/or propylene can be polymerized to produce polymer, such as polyethylene, polypropylene, ethylene-propylene copolymer, etc. C2+ olefins can be produced in conventional process; e.g., by one or more of catalytically converting alcohol, such as methanol; pyrolysing a hydrocarbon-containing feed, as in steam cracking; or catalytically cracking a hydrocarbon feed, as in fluidized catalytic cracking, hydrocracking, etc. Besides C2+ olefins, effluents from these processes can contain acidic gases, e.g., H2S and/or CO2. When the feeds to these processes contain sulfur and/or sulfur-containing molecules, such as in the catalytic cracking and/or steam cracking of crude oil and/or one or more fractions thereof, the acid gases generally include H2S. Especially when steam cracking is utilized for producing the C2+ α-olefins, the effluent can also contain aldehyde, such as acetaldehyde.
It is conventional to utilize amine for removing one or more acid gases from a process stream containing C2+ olefins. For example, CO2 and H2S can be removed from a steam cracker effluent by contacting the effluent with caustic and/or amine, e.g., by an acid gas scrubbing process in caustic or amine towers. It has been observed that such acid gas scrubbing leads to foulant precursor formation, e.g., by condensation reactions of carbonyl compounds. Undesirable polymerization of the foulant precursors can foul and obstruct the flow of liquid through the acid gas removal system, especially during regeneration of the scrubbing solution.
One way to remove foulant precursors and foulants, and to lessen fouling during the regeneration, involves contacting the amine with an aromatic stream such as pyrolysis gasoline to remove a majority of the foulant and foulant precursors upstream of the regenerator. Foulant and foulant precursors are transferred to the aromatic stream, producing a rich aromatics stream which is conducted away from the process. Any remaining foulant precursors can then be removed in the regenerator. See, e.g., U.S. Pat. Nos. 3,926,591 and 7,575,669, which disclose conducting the rich aromatics stream to waste or an oil scrubbing column. Conducting away the rich aromatic stream entails disposal and operational difficulties. Moreover, disposing of the rich aromatic stream represents the loss of a valuable, aromatic-containing product. A process is therefore desired which removes foulants and foulant precursors from a scrubbing solution and which disposes of fewer aromatic hydrocarbons than the conventional processes.